Infusion of fluids, such as drugs and plasma, into a patient is desirable in the medical field. Two common infusion methods are intravenous delivery of fluids by gravity and either intravenous or in arterial delivery by mechanically pressurizing the fluids for delivery to the patient using infusion pumps. Modern infusion pumps typically administer mechanical forces to the exterior a disposable device, such as a flexible plastic cassette or a flexible plastic tubing connected upstream to a medical fluid bag and downstream to the patient.
In a cassette type infusion pump, disposable cassettes have been advantageously employed for providing a simple disposable element in combination with a relatively straightforward pumping action. The cassette for this type of pump typically has one or more interconnected pumping chambers, and input and output tubing. The cassette and tubing are placed into contact with the pump or a pumping mechanism so that the contents or medicinal fluid pumped through the cassette and tubing are maintained in a sterile condition.
In another type of infusion pump, the pumping mechanism engages directly onto the tubing acting thereon with sequential compression forces to move the fluid through the tubing to the patient. This is called a peristaltic pump. Once again, the tubing set connected to the desired supply of medicine is inserted into the pumping mechanism maintaining a sterile condition of the medicinal fluid. Maintenance of a sterile condition is facilitated by disposing of the medicinal tubing set and simply replacing it with a newly sterilized and filled set as additional quantities of fluid are to be infused or when a new medicine is provided to a new patient.
Thus, disposable infusion tubing sets and disposable cassette sets are currently the standard of the industry for infusion flow control, whether through cassette pumps or through peristaltic pumps. One prior cassette pump and safety flow clip was designed for receiving the safety flow clip attached to the output tubing of a disposable cassette. Such a device is disclosed in U.S. Pat. No. 5,437,635, inventors Fields, et al., issued Aug. 1, 1995. The flow clip was designed to permit the operator to stop flow of fluids through the disposable cassette whether it was in or out of the pump. Also the receiving mechanism and flow clip were designed such that the cassette or the tubing set could not be installed unless the safety flow clip was in place. Flow was automatically closed if the cassette was not held in the proper operable pumping position. The cassette could not be removed until the flow clip was closed. Still the safety clip on the cassette could be manually moved from closed to open flow when the cassette was removed from the pump. The cassette set was also installable into the pump whether the safety clip was closed or open.
Of concern with respect to medical infusion pumps, whether cassette pumps or peristaltic pumps, is that the pumping capability and the accuracy of the pumps can depend in large part upon the size and functional characteristics of the cassette or tubing set. The functional characteristics can be affected by thickness, type of material, volume, resilience or any number of other features of the cassette or the tubing set. Thus, the use of one pumping cassette or one tubing set having particular size and functional characteristics can be properly calibrated for accurate, safe and controlled pumping and the use of another set with different size or different functional characteristics can be improper, inaccurate and possibly dangerous to the patient, unless the pumping parameters are appropriately adjusted to the different size and functional characteristics. Currently there is no known device or system that might automatically prevent such mismatching. The industry is currently relying on the ability of operators to distinguish size and on labeling and the competency of the operators to avoid this potentiality.